title: Mandatory contrast-enhanced venography to detect deep-vein thrombosis (DVT) in studies of DVT prophylaxis: upsides and downsides.
abstract: The introduction of venography into patient care was a major advance because it was the first accurate method for the diagnosis of DVT. Compression ultrasound has since become the preferred test for patients with suspected DVT because, unlike venography, it is simple, non-invasive and widely available. Venography has facilitated the development and approval of new anticoagulants and remains widely used as an efficacy outcome in trials of venous thromboembolism prevention. Most thrombi detected by screening venography are, however, small and unimportant for patients. In order to calculate the trade-off between an asymptomatic thrombus and a bleed we require an estimate of the number of asymptomatic thrombi that must be prevented to avoid a patient-important thrombus. A credible estimate of this ratio is not available. Therefore when used as a measure of efficacy in trials of thromboprophylaxis, venography has limitations for comparing the relative effects of alternative antithrombotic agents on outcomes important to patients.
authors.forename: Jack
authors.initials: J
authors.lastname: Hirsh
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Ginsberg
authors.forename: Noel
authors.initials: N
authors.lastname: Chan
authors.forename: Gordon
authors.initials: G
authors.lastname: Guyatt
authors.affiliation: John W. Eikelboom, Department of Medicine, McMaster University, Hamilton General Hospital, 237 Barton Street East, Hamilton, Ontario, L8L 2X2, Canada, E-mail: eikelbj@mcmaster.ca.
authors.forename: John W
authors.initials: JW
authors.lastname: Eikelboom
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use; D002309:Cardiology / Q000379:methods; D002986:Clinical Trials as Topic; D003287:Contrast Media; D017984:Enoxaparin / Q000627:therapeutic use; D005343:Fibrinolytic Agents / Q000627:therapeutic use; D000077425:Fondaparinux; D006470:Hemorrhage; D006801:Humans; D010690:Phlebography / Q000379:methods*; D011134:Polysaccharides / Q000627:therapeutic use; D015203:Reproducibility of Results; D013927:Thrombosis / Q000188:drug therapy / Q000517:prevention & control; D016896:Treatment Outcome; D020246:Venous Thrombosis / Q000175:diagnosis* / Q000473:pathology* / Q000517:prevention & control
chemical_list: D000925:Anticoagulants; D003287:Contrast Media; D017984:Enoxaparin; D005343:Fibrinolytic Agents; D011134:Polysaccharides; D000077425:Fondaparinux
keywords: Deep-vein thrombosis; prophylaxis; venous thrombosis